The field of this invention relates generally to wind turbine blades, and more particularly to blades including damping elements that facilitate reducing the noise generated by the blades during operation of the wind turbine.
Wind turbines use wind energy to generate electricity. Known wind turbines include a tower, a nacelle coupled to the tower, and a rotor having a hub and blades coupled to the nacelle. Wind causes the blades and hub of the rotor to rotate with respect to the nacelle thereby creating mechanical energy that is transferred by a generator into useable electrical energy. At least some known utility grade wind turbines (i.e., wind turbines designed to provide electrical power to a utility grid) use long rotor blades (e.g., 30 meters or more in length).
However, at least some known wind turbines may generate unacceptable levels of noise during their operation, especially when the wind turbines generators are located in close relation to populated areas. A portion of the noise emitted by wind turbine can be attributed to the rotation of the blades. At least some known blades emit noise by displacing and scattering highly turbulent air during rotation. In addition, at least some blades are formed with a hollow interior, and such blades may emit noise during operation that generates within the interior of the blade. For example, noises may promulgate from one or more of various mechanical components (e.g., a gear box housed in the nacelle) of the wind turbine. Such noises may resonate within the hollow interior of the blades.
In addition, loose debris within the interior of the blade (e.g., dried or loose adhesive) may tumble from one end of the blade to the other during rotation of the blade. Specifically, as it tumbles, the debris hits against the interior surface of the blade generating additional noise, such noise generation is sometimes referred to as the “rainstick effect”. In addition to noise concerns, the debris hitting against the interior surface of the blade may cause structural damage to the blade.